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driving lights and headlight bridge

Printed From: the12volt.com
Forum Name: Relays
Forum Discription: Relay Diagrams, SPDT Relays, SPST Relays, DPDT Relays, Latching Relays, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=33327
Printed Date: May 04, 2025 at 8:55 PM


Topic: driving lights and headlight bridge

Posted By: theophile
Subject: driving lights and headlight bridge
Date Posted: June 04, 2004 at 9:44 PM

I've got a car with separate bulbs for high and low beams (9005/9006) and I also have a set of driving lights installed. My headlight switch has 3 positions: Off, parking lights, headlights & parking lights. With the headlights on, I have the option of low beams or high beams. While one is on, the other shuts off.

I would like the following behavior:

When the switch is turned onto the parking lights position, the driving lights come on as well. They would therefore also be on in the headlights position.

When I have the car's low beams on, only the low beams illuminate. But when I switch to high beams, the high beam lights come on in addition to the lows. This way I can still have the road in front of me lit up.

I have a standard automotive relay which I had been using for my driving lights before I swapped out my composite headlights this afternoon. I have since become confused as to the proper wiring of this relay.

30 is the +12V from the battery, yes? On which line should I connect the "trigger" wire from the parking lights? Is it 86, and then I connect the + line of the driving lights to 87? And 85 is ground?

The other reason I am posting this is to find out if there is a better way to achieve this behavior than using two relays independently wired.

Basically, if this were your car, how would you go about doing this?

Thanks!



Replies:

Posted By: civichater
Date Posted: June 14, 2004 at 11:45 AM

This is a pretty easy set-up. 

DRIVING LIGHTS--

30 = 12v from battery  87=output to driving lights   85= trigger from parking lights  86=either 12v or ground depending on the trigger (if the parking light wire is 12v, then 86= ground.  If the parking light wire is ground, then 86=12v) 87a=not used

High beams--

Considering that both the high and low beam are positive trigger--                       

30=12v    87=output to lowbeam wire  85=trigger from high beam wire  86=ground  87a=not used

remember to always fuse 12v on 30 

Considering that both high and low beam are negative trigger--

30=ground   87=output to low beam wire  85=trigger from hige beam wire   86=12v   87a=not used

Hopes this helps






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